The present invention relates to a manufacturing method and article produced thereby, and more particularly to a method of manufacturing a three-dimensional structure having hollow portions and structures produced in accordance with the method.
In order to produce an integrally molded product, various molding techniques have been conventionally employed. Blow molding offers one way in which a hollow product is produced. In accordance with such approach, a “bubble” of plastic is expanded into a shaped mold cavity, thereby assuming a hollow form corresponding to the interior topography of the cavity walls. While effective for producing structures having a relatively thin wall, such as bottles and the like, blow molding cannot be used to produce structures having substantial thickness. The process is further limited to the extent that if openings in the hollow structure were desired, such as provided to form an open frame structure, an additional fabrication step would be required.
Rotational molding (roto-molding), a process which involves rotation of a mold to deposit molding material on an interior of a mold has been used to produce various hollow structures, but is also limited with regard to what materials can be used in the molding process, and generally involves relatively long cycle times. As with blow molding, finishing of the molded articles, particularly those with openings defining a frame structure, generally requires additional steps after molding.
Notwithstanding the above approaches, it has remained difficult heretofore to produce a structure having hollow inner portions which is integrally molded as a single part, particularly utilizing injection and compression molding techniques.
It would therefore be desirable to provide a method of molding structures having hollow interior portions which is applicable to injection molded and compression molding processes.
Accordingly, it is an object of the invention to provide a molding method for hollow articles of integral unitary structure which overcomes the drawbacks of the prior art, and which is applicable to injection and compression molding techniques.
It is a further object of the invention to provide an article of unitary structure which includes a hollow portion inward of a portion of the structure comprising the article.